1. Field of the Invention
The present invention relates to a liquid discharge head which discharges liquids, such as ink, and an ink jet recording apparatus including the liquid discharge head.
2. Description of the Related Art
As liquid discharge heads provided in an ink jet recording apparatus, there is a liquid discharge head in which a heat generating element (heater) and its driving circuit, and line which connects the heat generating element and the driving circuit are formed on the same substrate, using a semiconductor processing technique. Moreover, there is also a liquid discharge head in which a temperature detecting element which is close to a heat generating element and in which an output voltage changes in response to the temperature change of the heat generating element is formed.
In ink jet recording apparatuses including the above liquid discharge heads, in order to increase the speed of recording operation, the number of heat generating elements to be formed on a substrate tends to increase. This is because, as the number of heat generating elements increases, the number of discharge ports provided to face the heat generating elements also increases, and consequently, it is possible to discharge a large amount of ink at one time. However, in a case where a current is simultaneously applied to a number of heat generating elements, a pulsed large current (a current of about 1 A to several amperes) flows to an electrical power source line and grounding line. As such a pulsed large current flows, noise caused by inductive coupling may be generated in a signal line of the above driving circuit. In this case, there is a concern that the driving circuit may malfunction due to the noise.
Thus, a liquid discharge head for solving such a problem is disclosed in Japanese Patent Application Laid-Open No. 2000-127400. In the liquid discharge head disclosed in Japanese Patent Application Laid-Open No. 2000-127400, the laying of a signal line which is easily influenced by noise is suppressed to the minimum by arranging a driving circuit (signal processing circuit) at a corner portion of a substrate.
In the ink jet recording apparatus, conventionally, temperature detection (current application of a temperature detecting element) of a heat generating element is performed while a current is not applied to the heat generating element, that is, during non-recording. However, in recent years, performing temperature detection during recording has been required in order to further increase the speed of a recording operation. This is because, by performing recording while performing temperature detection, it is possible to assign the time for the temperature detection spent during non-recording to other processes. However, in a case where temperature detection is performed during recording, as described above, a pulsed large current flows to the electrical power source line and grounding line for applying a current to the heat generating element. Therefore, it is assumed that noise is generated in an electrical line for applying a current to the temperature detecting element. In this case, there is a concern that the output voltage of the temperature detecting element may be influenced by noise, and the temperature of the heat generating element may be erroneously detected. In addition, although Japanese Patent Application Laid-Open No. 2000-127400 discloses a technique in which a driving circuit is not easily influenced by noise, a technique of coping with erroneous detection of the temperature of the heat generating element described above is not disclosed.